Twofold rotation.
The existence of the mass term guaranteeing the existence of weak and second-order topological phases for both pairing symmetries characterized by the phase \(\phi = 0\)  and \(\pi \)  follows from results of Refs. [1]}, [2]}, as detailed in the last paragraph of Sec. REF . For concreteness, for \(\phi = 0\)  we may choose the representations \(U(\mathcal {R}_\pi )= i \tau _2\) , \(\mathcal {P} = K\)  where the mass term that gaps a pair of symmetry related Majorana bound states is \(\tau _2\) . For \(\phi = \pi \)  we may choose the representations \(U(\mathcal {R}_\pi )= i \tau _2\) , \(\mathcal {P} = \tau _3 K\)  where no mass term exists. Refs. [1]}, [2]} also show that a Chern superconductor with odd Chern number exists only for \(\phi = 0\)  while for \(\phi = \pi \) , the Chern number is constrained to be even.
